Antigen stimulation of rat basophilic leukemia (2H3) cells is associated with increase in intracellular calcium (Ca signal), substantial phosphatidyl inositol (PI) breakdown as well as histamine release. Different clones of the RBL cells, however, showed varied responses to antigen from none at all to about 80% of the responses observed in 2H3 cells. In partially defective clones, PI breakdown and calcium signal were more transient than was observed in 3H3 cells. In all but one of these clones the Ca signal and PI breakdown were correlated. The exception was a clone in which PI breakdown and histamine release but not calcium signal were observed. In 2H3 cells PI breakdown the Ca signal and histamine release were highly temperature dependent. There was no response below 20 degrees C and a maximal response at 36-37 degrees. At temperatures about 37 degrees the responses were suppressed and by 40-42 degrees they were completely inhibited. The effects of temperature were reversible. The findings confirm previous data that although PI breakdown and calcium signal are in general highly correlated, PI breakdown can occur independently of calcium signal.